Problem: What is the least common multiple of 15 and 40? Another way to say this is: $\lcm(15, 40) = {?}$
The least common multiple is the smallest number that is a multiple of 15 and 40. We know that 15 x 40 (or 600) is a common multiple, but is it the least common multiple? Write out the multiples of 40 until we find a number divisible by 15. 40, 80, 120, So, 120 is the least common multiple of 15 and 40.